1. Field of the Invention
This invention relates to organosilicate materials.
2. Description of the Related Art
Some techniques use structured phases of amphiphilic block copolymer molecules as templates for fabricating polymeric materials with mesoscopic structures. The block copolymer molecules self-assemble into stable structures with mesoscopic structures when their concentrations and temperatures are in specific ranges. Since block copolymer molecules have phases with different types of mesoscopic structure, these template-based techniques have been used to fabricate polymeric materials with a variety of types of mesoscopic structures.
Typical template-based methods involve several fabrication steps. The methods include making a starting solution that contains both block copolymer molecules and monomers for making the desired material. In the starting solution is a uniform solution of the two types of molecules. The methods include evaporating solvent from the starting solution until the concentration of block copolymer molecules achieves a concentration for which the stable phase for block copolymer molecules has a nontrivial mesoscopic structure. At this concentration, the block copolymer molecules self-assembly into the nontrivial structure. Self-assembly by the block copolymer molecules causes the monomers, which are intermixed with the block copolymer molecules, to also condense into a similar or different mesoscopic structure. The methods include heating the material with the mesoscopic structure to polymerize the monomers into a solid whose structure is fixed by the condensation.
The template-based methods have used alkoxide monomers to fabricate polymeric materials with a variety of morphologies. These morphologies include spherical, cylindrical, lamellae, and gyroid structures. But, the alkoxide precursors typically produce polymeric materials wettable by water.
Various embodiments of template-based methods fabricate organosilicate materials with mesoscopic structures from precursors having hydrophobic moieties. The hydrophobic moieties can cause changes to affinities towards water during curing, e.g., due to shedding of reactive hydrophilic moieties. Such changes can destroy template-induced structures, which are based on interactions between hydrophilic and hydrophobic moieties. The affinity changes can cause precursors to phase separate so that the previously produced mesoscopic structures are destroyed. Curing-induced phase separations have impeded the successful use of alkoxide precursors having hydrophobic moieties in the production of materials with mesoscopic structures.
Various embodiments eliminated curing-induced destruction of mesoscopic structures by using precursors that remain amphiphilic during curing. In particular, the precursors include both hydrophobic and hydrophilic moieties, and the respective hydrophobic and hydrophilic characters of these moieties are unchanged by the curing reactions that crosslink composites. Thus, crosslinking does not cause drastic changes in molecular affinities of the organosilicate precursors.
One embodiment features a template-based method for fabricating an organosilicate material with a mesoscopic structure. The method includes providing a solution of an amphiphilic template molecules, mixing amphiphilic organosilicate precursors into the solution to form a mixture, and evaporating solvent from the mixture. The evaporation produces a composite in which the amphiphilic organosilicate precursors have a nontrivial mesoscopic structure.
Another embodiment features a solid that includes crosslinked amphiphilic organosilicate precursors. The amphiphilic organosilicate precursors form a matrix with an array of micro-structures dispersed in the matrix.